Coronary Artery Disease

Coronary Artery Disease: Description:

Coronary disease (or coronary heart disease) refers to the failure of the coronary circulation to supply adequate circulation to cardiac muscle and surrounding tissue. It is sometimes equated with atherosclerotic coronary artery disease, a condition in which the arteries that supply blood to the heart become clogged and disrupt the normal blood supply to the heart muscle. CAD is usually caused by atherosclerosis, a condition in which a substance called "plaque" builds up in the blood vessels. Without adequate blood, the heart becomes starved of oxygen and the vital nutrients it needs to work properly. This can cause chest pain called angina. When one or more of the coronary arteries are completely blocked, a heart attack (injury to the heart muscle) may occur.

What causes the coronary arteries to narrow?

Your coronary arteries are shaped like hollow tubes through which blood can flow freely. The walls of the coronary arteries are normally smooth and elastic.

Coronary artery disease starts when you are very young. Before your teen years, the blood vessel walls begin to show streaks of fat. As you get older, the fat builds up, causing slight injury to your blood vessel walls. In an attempt to heal the blood vessel walls, the cells release chemicals that make the blood vessel walls stickier.

Other substances traveling through your bloodstreams, such as inflammatory cells, cellular waste products, proteins, and calcium, begin to stick to the vessel walls. The fat and other substances combine to form a material called plaque.

Over time, the inside of the arteries develop plaques of different sizes. Many of the plaque deposits are soft on the inside with a hard fibrous “cap” covering the outside. If the hard surface cracks or tears, the soft, fatty inside is exposed. Platelets (disc-shaped particles in the blood that aid clotting) come to the area, and blood clots form around the plaque.

This causes the artery to narrow even more. Sometimes, the blood clot breaks apart, and the blood supply is restored.

In other cases, the blood clot (coronary thrombus) may totally block the blood supply to the heart muscle (coronary occlusion), causing one of three serious conditions, called acute coronary syndromes.

Symptoms:

The symptoms and signs of coronary artery disease are noted in the advanced state of disease, most individuals with coronary artery disease show no evidence of disease for decades as the disease progresses before the first onset of symptoms, often a "sudden" heart attack, finally arises. The disease is the most common cause of sudden death and is also the most common reason for the death of men and women over 20 years of age. As the degree of coronary artery disease progresses, there may be near-complete obstruction of the lumen of the coronary artery, severely restricting the flow of oxygen-carrying blood to the myocardium. Individuals with this degree of coronary artery disease typically have suffered from one or more myocardial infarctions (heart attacks) and may have signs and symptoms of chronic coronary ischemia, including symptoms of angina at rest and flash pulmonary edema.

Treatment:

Therapeutic options for coronary artery disease are based on three principles:

Extensive clinical and statistical studies have identified several factors that increase the risk of coronary heart disease and heart attack. Major risk factors are those that research has shown significantly increase the risk of heart and blood vessel (cardiovascular) disease. Other factors are associated with increased risk of cardiovascular disease, but their significance and prevalence haven't yet been precisely determined. They're called contributing risk factors.

The American Heart Association has identified several risk factors, some of them can be modified, treated or controlled, and some can't. The more risk factors you have, the greater your chance of developing coronary heart disease. For example, a person with total cholesterol of 300 mg/dL has a greater risk than someone with total cholesterol of 245 mg/dL, even though everyone with total cholesterol greater than 240 is considered high-risk.

What are the major risk factors that can't be changed?

Increasing age — Over 83 percent of people who die of coronary heart disease are 65 or older. At older ages, women who have heart attacks are more likely than men are to die from them within a few weeks.

Male sex (gender) — Men have a greater risk of heart attack than women do, and they have attacks earlier in life. Even after menopause, when women's death rate from heart disease increases, it's not as great as men's.

Heredity (including Race) — Children of parents with heart disease are more likely to develop it themselves. Most people with a strong family history of heart disease have one or more other risk factors.

What are the major risk factors you can modify, treat or control by changing your lifestyle or taking medicine?

Tobacco smoke — Smokers' risk of developing coronary heart disease is 2-4 times that of nonsmokers. Cigarette smoking is a powerful independent risk factor for sudden cardiac death in patients with coronary heart disease; smokers have about twice the risk of nonsmokers. Cigarette smoking also acts with other risk factors to greatly increase the risk of coronary heart disease. People who smoke cigars or pipes seem to have a higher risk of death from coronary heart disease.

High blood cholesterol — As blood cholesterol rises, so does the risk of coronary heart disease. When other risk factors (such as high blood pressure and tobacco smoke) are present, this risk increases even more. A person's cholesterol level is also affected by age, sex, heredity, and diet.

Physical inactivity — An inactive lifestyle is a risk factor for coronary heart disease. Regular, moderate-to-vigorous physical activity helps prevent heart and blood vessel disease. The more vigorous the activity, the greater your benefits. However, even moderate-intensity activities help if done regularly and long term. Physical activity can help control blood cholesterol, diabetes, and obesity, as well as help lower blood pressure in some people.

Obesity and overweight — People who have excess body fat — especially if a lot of it is at the waist — are more likely to develop heart disease and stroke even if they have no other risk factors. Excess weight increases the heart's work. It also raises blood pressure and blood cholesterol and triglyceride levels and lowers HDL ("good") cholesterol levels.

What other factors contribute to coronary heart disease?

Individual response to stress may be a contributing factor. Some scientists have noted a relationship between coronary heart disease risk and stress in a person's life, their health behaviors, and socioeconomic status. For example, people under stress may overeat, start smoking or smoke more than they otherwise would, drinking too much alcohol can raise blood pressure, cause heart failure and lead to stroke.

Diagnosis:

To diagnose CAD, the following may be helpful:

The diagnosis of angina is based mainly on your description of symptoms and precipitating factors. Other medical conditions, such as hypertension or diabetes, increase the risk of CAD.

Physical examination — Since high cholesterol is a risk factor for CAD, doctors will look for evidence of elevated cholesterol, such as a collection of fatty tissue near the eyes (xanthoma). Your doctor will also listen for extra sounds in the heart, known as murmurs or gallops, which may suggest heart disease.

Blood tests — Increased levels of total cholesterol, triglycerides, and blood sugar are risk factors for CAD, as are increased levels of homocysteine (an amino acid) and c-reactive protein. Angina may be precipitated or worsened by anemia, overactive thyroid, and kidney failure. Testing for the presence/quantity of heart muscle enzymes in the blood may indicate heart muscle damage.

Electrocardiogram (EKG) — Electrodes are attached to your skin to record the electrical activity of your heart. This test can identify heart rhythm problems and damage to your heart caused by a previous heart attack. During the anginal attacks, the EKG may show specific changes. Using this test to diagnose CAD has its limitations because other heart problems can also cause changes in the heart's electrical waves.

Stress test — Stress tests will show how well the heart is functioning. Depending on your health, you may take a stress test involving exercise (sometimes on a treadmill) or take medication that will increase blood flow to the heart. You may be hooked up to an EKG or another heart monitor. If the exercise or medication causes an increased need for blood flow that the blood vessels diseased by CAD cannot accommodate, the EKG will appear abnormal. Also, a radioactive tracer can be injected so the doctor will be able to see which parts of the heart are not getting an adequate blood supply.

Nuclear scanning — With this test, your doctor can see damaged areas of the heart and examine the heart's pumping action. A small amount of radioactive material is injected into one of your veins, usually in the arm. The healthy heart muscle takes up this material. Then, a scanning camera reads where the material does or does not show up. This determines which areas of the heart muscle have been previously damaged.

A variety of imaging techniques may be used to examine the heart muscle after the radioactive material has been injected. These include scintigraphy, computed tomography (CT) scan, magnetic resonance imaging (MRI), positron emission tomography (PET) scan, and single-photon emission computerized tomography (SPECT) imaging. Nuclear scanning can be performed with the patient at rest, immediately following exercise, or after the administration of a medication that simulates the stress of exercise.

Echocardiogram — An ultrasound image of the heart demonstrates the heart muscle's movement with each heartbeat. When the heart doesn't get enough blood, the walls of the heart show irregular motion. The echocardiogram can be performed at rest, during exercise, or after the administration of medication that simulates the stress of exercise.

Coronary angiography — Also called cardiac catheterization, this is the most accurate way to measure the severity of CAD. It is also the most expensive and invasive method. A thin tube (catheter) is put into an artery of the arm or leg and passed through the body into the arteries of the heart. A dye is injected through the catheter and into the heart's arteries. Several x-ray images are taken. These pictures will show the amount of blockage caused by atherosclerosis.

Developing technologies include the following:

Magnetic resonance angiography (MRA) — The MRA test uses MRI technology to identify coronary artery blockages. This technique has its limitations and is not commonly used.

Electron beam CT scan (EBCT) — This is a “heart scan” that uses some radiation to detect tiny calcium deposits in the lining of the coronary arteries. This technique is appealing because it is not invasive, physically exerting, or risky. However, results can often be incorrect or misleading, so research is still being done on EBCT.

Computed tomography angiography (CTA) — CTA uses 64 slices CT imaging—along with an IV contrast injected in the hand or arm—to image the coronary arteries and look for blockages. This test is similar to coronary angiography but poses less risk because there is no need for invasive catheter placement.

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